In recent years, there have been widely developed, in various fields, a knowledge engineering applied expert system which makes use of the concept of AI (Artificial Intelligence). This system is intended to extract solutions or failures for an inquiry from the experiences already stored and to display and output them, or further, to control a variety of subjects by means of a computer. For realizing this system, the most serious problem resides in the difficulty of collecting past experiences of the experts or operators massively and accurately as knowledge. This cause will be examined in case the expert system is applied to the operation of a subject of control. 1. For experiences of medium- or large-scale accidents, records are complete, and the operator's memory is clear. Nevertheless, it is usual that small-scale accidents or minor events are neither recorded nor remembered clearly. 2. The operator himself to supply the knowledge is not convinced that his daily minor experiences are worth being stored in the computer so that they may be used as the knowledge of the expert system.
Here, the medium- or small-scale accidents are experienced a little, and these special events could not constitute an effective knowledge group. Since, moreover, the expert system to be applied to such a subject should ensure the operation without any accident, the knowledge should be collected from the rather minor events to be experienced in daily operation, such as the small-scale accidents.
There are known in the prior art several methods for collecting knowledge dictating how the expert himself reacts and behaves against the situations set by the computer. For example, Japanese Patent Laid-Open No. 60 - 203576 discloses an invention which is directed to a system for acquiring train rules for making a railway diagram. The knowledge engineer or expert himself simulates and displays the situation of an abnormal state (e.g., the disturbances of the diagram) by setting the abnormal state so that his knowledge may be smoothly extracted as if he actually faces the practical problem. Japanese Patent Laid-Open No. 59 - 167771 discloses a system for acquiring knowledge by creating "questions" for searching ultimate causes by use of the knowledge relations systemized by the structuring method and in cooperation with the specialists. However, this system finds it difficult to make the questions and is accompanied by a problem that it cannot acquire much knowledge information efficiently according to the real operation of the subject of control.